portable audio mixer

hey everybody
I had a little idea but i am not so good in this sort off things is it possible to make an portable audio mixer on batteries for mixing with 2 mp3-players if someone has an idea can he tell me how to make this it should be great because I always play music with my friends but it should be nice if we can mix music
(I am sorry for my bat English I am from belguim)
Sompie